A garage door seal never makes the shortlist when people talk about home security or automation, yet it is the component that touches the concrete several times a day and decides whether the garage stays dry in a January thunderstorm. It is also the part most likely to be cracked, flattened and quietly failing while everything else on the door works perfectly. This guide covers what the seals on a typical South African garage door actually do, the four common types, how to tell when yours are finished, and what replacement honestly costs.
One distinction up front, because it gets muddled in hardware-store aisles: seals and insulation are different products for different problems. A seal keeps weather out — water, dust, wind-blown leaves, insects. Insulation slows heat moving through the door, which is a comfort question for the rooms above or next to the garage. Our garage door insulation guide covers that side; this article is about the rubber.
The Four Jobs, and the Four Types
A healthy seal does four jobs at once. It blocks water driven under the door by a summer thunderstorm. It blocks the fine dust a Highveld winter deposits through any gap wide enough to see daylight. It blocks pests — the mice and cockroaches that treat a 15 mm gap as an invitation, a problem our pest damage guide covers from the motor’s point of view. And it calms the door: a sealed opening rattles less, whistles less and stops water ponding inside on the floor.
| Type | Where it fits | Best at | Watch out for |
|---|---|---|---|
| Bottom seal (retainer + bulb) | Channel along the door’s bottom rail | The main dust and water barrier | Wrong-profile bulb; flattened sections on uneven floors |
| Bottom flap (PVC) | Glued or screwed flap on older doors | Cheap, fits any door | Adhesive fails in sun; drags on rough concrete |
| Perimeter seal | Up the jambs and across the lintel | Wind-driven rain around the sides | Gaps where two runs meet at a corner |
| Threshold kit | Glued to the floor where the door lands | Uneven or sloped driveway aprons | Needs clean, sound concrete; a trip edge if too tall |
Most sectional doors leave the factory with a retainer-and-bulb bottom seal and nothing else; perimeter sealing is an add-on that earns its cost on exposed, west-facing openings where driving rain finds its way around the sides. Brush seals, common on commercial doorways, suit high-cycle openings with uneven floors but collect grit and stiffen over the years — for homes they are the exception, not the default.
How to Tell the Seals Are Done
The test costs nothing: close the door in daylight and look along the floor. A thin, even line of light is normal on anything short of a perfect slab; separate pools of daylight mean the seal has given up. The sharper version is the paper test — close the door on a sheet, then pull. Paper that slides out with no resistance is a failed seal; paper that grips or tears still has life in it.
The confirming signs follow within a season. Dust lines just inside the opening. A damp patch or standing water after summer storms — the reason our storm season guide lists the seals as a pre-summer check. Droppings or nesting material in corners, because pests got in somewhere. And the seal itself tells you when you look: healthy rubber is springy and dark; finished rubber is hard, pale, cracked across the bulb, or flat where it should be round. UV is the killer — north- and west-facing doors age their seals fastest, and a seal that still looks present often has the give of a sun-baked tyre.
Replacing a Bottom Seal: DIY or Installer
The job splits cleanly down the middle. If your door has a retainer channel, replacement is a genuine owner job: slide out the old bulb (often held by two end screws), cut a short sample of it or measure its width and profile, and slide the new one in. The only trap is ordering by eye — bulbs come in several profile shapes that look identical in a bin and fit exactly one retainer each. Match the old part, not the photo on the packet.
Glued flap seals and threshold kits are where DIY enthusiasm usually stalls. Both live or die by surface preparation — the concrete a threshold bonds to must be clean, dry and sound, and a dusty, painted apron will release the kit within one winter. There is also a diagnosis step people skip: a visible gap in one corner is usually a door or floor problem, not a seal problem. Sectional doors sit in tracks that drift with time and knocks, and driveway aprons pour unevenly. Fitting a thicker seal to compensate loads the door unevenly; the correct sequence is checking the door sits level in its tracks — part of the annual once-over in our maintenance checklist — and only then choosing the seal. Where the floor itself is the culprit, a threshold kit turns a sloped apron from a permanent drip point into a non-event, which is a far better spend than a third bulb in two years.
What It Costs
As a guide rather than a quote: a replacement bulb for a standard retainer is a small spend — the kind of part that costs less than the petrol to fetch it. A complete bottom assembly (retainer, bulb, fixings) for a standard double door sits in the low hundreds of rand. A floor threshold kit lands in the mid hundreds, and a professional refit — seal plus perimeter runs, plus the alignment check that should always accompany it — prices as a short call-out, in the same band as other hardware work in our Pretoria cost guide. If the door is due for replacement anyway after storm or impact damage, our panel repair guide explains when new seals simply arrive with the new door.
Two economics notes. First, seals are the cheapest weatherproofing this house will ever get: given what a wet garage does to tools, shelving and the stored boxes nobody has opened since the move, nothing else in maintenance has a better ratio of cost prevented to cost spent. Second, a neglected bottom seal lets water sit against the door’s lowest rail, and on steel doors that rusts the panel from the inside out — a small part quietly becoming the argument for a whole new door.
Frequently Asked Questions
How often should garage door seals be replaced?
Plan on every three to five years for the bottom seal — sun exposure decides more than usage does. Inspect annually as part of a service; perimeter seals often outlast the bottom because they take no compression.
Can I replace the bottom seal myself?
Yes, if the door has a retainer channel — it is a slide-in job once you have the correct replacement profile. Glued flaps and floor thresholds punish preparation shortcuts, and a corner gap usually needs an alignment check first, not a thicker seal.
Why is there a gap at one corner when the rest seals fine?
Almost always the floor or the door, not the seal: aprons pour unevenly and sectional doors drift in their tracks over the years. Get the door sitting level first, then use a threshold kit if the floor itself is the culprit.
Do garage door seals keep mice out?
A sound bottom seal closes the gap mice and cockroaches actually use, so it is the single most effective pest-proofing on a garage door. It adds little to break-in resistance though — that is a panel and locking question, not a rubber one.
If the paper test fails and you would rather not guess at profiles, send us the door’s brand, a photo of the bottom rail and the gap you are seeing — we arrive with the common retainer profiles on the van and check the door’s seating while we are there.